. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 665 shoulder girdle consists only of the cartilaginous portion (scapula-coracoid); the region of the shoulder girdle is covered like the rest of the body by placoid scales. "When dermal ossifications appear on the skull we also find such ossifications on the cartilaginous shoulder girdle. In the Sturgeons (Chondroganoidei) for instance we find two such ossi- fications covering the cartilaginous scapula-coracoid of both sides. The lower ossification; the larger one was formerly called the infraclaviele, the upper smaller
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 665 shoulder girdle consists only of the cartilaginous portion (scapula-coracoid); the region of the shoulder girdle is covered like the rest of the body by placoid scales. "When dermal ossifications appear on the skull we also find such ossifications on the cartilaginous shoulder girdle. In the Sturgeons (Chondroganoidei) for instance we find two such ossi- fications covering the cartilaginous scapula-coracoid of both sides. The lower ossification; the larger one was formerly called the infraclaviele, the upper smaller one the clavicle, by Gegenbaur. These two ossifications are also found in the Crossopterygians (Polypterus and Calamoichthys) and the Dipnoi. By a comparison of these forms with the Stegocephali Gegenbaur reached the conclusion, that the lower element (infraclavicle) of the Crossopterygii and Dipnoi is homologous to the clavicle of the Stegocephali; the upper piece (cla- vicle) to the dermal bone in the Stegocephali, named scapula, prae- coracoid or clavicula. For this element he introduces the name Cleithrum. The true clavicle of the fishes mentioned is the clavicle, the bone formerly called clavicle is the cleithrum of the Stegocephali. In the Rhomboganoidei (Lepidostei), Cycloganoidei (Amia) and the Teleostei the cleithrum alone is present, in the Amniota the Cleithrum is gone, but in the Stegocephalia, the Chondrostei, Dipnoi and Crosso- pterygii we have both clavicle and cleithrum. We shall now consider the conditions in the Stegocephali more fully. We always find one median and a pair of lateral dermal ele- ments on the lower side of the body behind the hyoid region. These were originally described as thoracic plates. They are homologous to the epiplastra and endoplastron of the Testudines. There is quite a considerable diversity in the form of these elements, as can be best seen from the figures (Fig. 4—8). The cleithrum (scapula praecoracoid, clavicle) is connected wi
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